Bad_Karma7

Ok, it idles fine (stable), little throttle and it revs up and down, jerking car back and forth. Not just a single hesitation. Seems to be running lean also .02 v on O2 voltage. Boost...I can hear the turbo spooling, BOV vents when I let off throttle, so I know I'm getting boost. But I don't feel the power. Also WOT revs but seems to hit a wall and not getting acceleration. Most of the search results refer to people having a single hesitation...mine is rhythmic. Just had injectors cleaned, Jacobs fc1000 ignition amp, checked coils, new plugs. Any clues guys?

dgeesaman

iTrader: (7)

You might be getting boost, but you won't know for a fact it's reaching the engine unless you measure it off the UIM with a boost gauge or the MAP. Boost leaks, faulty actuators, etc can cause such symptoms.

However, the O2 indications suggest you might have something getting in the way of complete fuel injection - low rail pressure, bad injector, etc. That will cause some pretty irritating hesitation and stumbling.

How was the car before this started to occur, what were you trying to do when it happened, and what are the mods?

Dave

Bad_Karma7

It ran fine before, there was vacuum leak, never did this kind of surging. I went in to replace FPD clean and flow test injectors (new gasket and air bleed valve), replaced all vacuum lines, new oil metering lines, checked all solenoids/new check valves, all gaskets were metal and in good shape, installed FC1000 ignition amp. Mods are cat back, down pipe, free flow intake. Can I measure boost/vacuum from UIM with my mityvac?

dgeesaman

iTrader: (7)

Yep, you can use a Mityvac, but it will either read pressure or vacuum, but not both at the same time. A fuel pressure gauge will often work too.

Unfortunately, I went thru all this this year, and it ended up being an injector problem. Injectors not injecting enough fuel will post no ECU codes, and they go lean at the worst possible time (under load). The car would buck under boost, adn buck repeatedly if I kept on the throttle. So watch you don't blow your engine if your o2 sensor indicates lean burn during the stuttering.

I had my injectors cleaned by a local shop who couldn't pre- and post-test to verify performance. It ended up that my injectors were not working right - the lesson I took is 1) never trust an FD injector and 2) only get them cleaned by a good company with FD injector experience, get before/after test results, and install them and run them asap after cleaning. I hope this isn't the problem for you.

Dave

Bad_Karma7

I had a before and after flow and leak test, they gave me a print out of the results. I think the Jacobs unit just fried my coil pack; I thought that issue was resolved! I have the latest Jacobs FC1000 (Just installed it). My coils were in spec. when I reinstalled, they were .7 ohms now they are 13 ohms. You think the coil burning out is what's causing this, or do you still think it's the injectors?

dgeesaman

iTrader: (7)

Well if your coil is giving different readings, definitely troubleshoot that first. I've never used an ignition amp, just stock stuff. I've heard that Turbo2 coils are a little tougher - you might try that this time around.

Who cleaned the injectors, and how long after until you got them installed and running?

Dave

Bad_Karma7

Injectors cleaned by witch hunter, installed 1 week after cleaning...didn't sit around for a month...was very careful about that. So, would bad coils cause this issue, or should I still look at injectors?

dgeesaman

iTrader: (7)

Coils can definitely cause it. Can you turn down the gain on that ignition amp?

Looks like you handled the injectors with due care - I would be certain your ignition issues are sorted before suspecting them.

Dave

Bad_Karma7

No, I don't see any way to turn down the gain on this unit. I just picked up a TII coil, now just have to figure out how to wire it and shove it in the stock location. I'm guessing that I need to cut the wire from the FD ignitor harness and route it to the ignitor on the TII coil. Does that sound about right? I really appreciate all your help.

You rock...

Bad_Karma7

Now what's going on? This may sound ignorant, I'm not a a mechanic by trade. I see a 14-17 vacuum at idle via a mytivac (need to adjust my idle a little), when I blip the accelerator...i get 20+ in vacuum. Shouldn't it go the other way into pressure reading? I'm confused.

By the way, I think I got the surging under control. Now I get no boost at all. I did have improved boost for a little while, now the boost went to the same place all my money and time has gone.

Bad_Karma7

It takes very little vacuum to open the BOV, if I'm seeing nothing but vacuum, then the BOV is always open and venting. I tested that by disconnecting the vacuum line from manifold. Sure enough it started to go from vacuum to almost 0 pressure. That explains why I'm not seeing any kind of boost. Now I just have to figure out why revving engine doesn't bring me towards positive pressure in manifold. Someone want to fill in the missing piece of this puzzle? Throw me a bone here guys...please.

dgeesaman

iTrader: (7)

Mityvacs can only read pressure or vacuum at once. Flip it to the pressure side and try again.

It is normal to see greater vacuum than idle levels when the engine revs are dropping.

Dave

Bad_Karma7

I did switch my mityvac to pressure...it still read vacuum, I took it off and plugged the mityvac and pumped to make sure it was reading pressure. I put it back on and all it showed was vacuum. The problem is that I read higher vacuum when I was revving, not when the revs were dropping.

DaveW

When you are at higher revs, you will read higher vacuum, as long as the engine is not under load. The higher revs mean less time for leakage past the seals to occur. You will read lower vacuum when the engine is under load (accelerating hard in neutral, or accelerating in gear). While the throttle is closed you will get still higher vacuum either coasting in gear or with the engine revs decreasing.

Bad_Karma7

I think I finally figured out this whole issue. I cleaned and lubricated the ISC, adjusted all idle settings, adjusted the TPS. Now here's the interesting part, it was still doing it, so I looked at voltage of TPS through the commander. The commander reported that the voltage was within spec, but it still didn't like it. I had to readjust the voltage to read higher, but stay within spec before the engine was happy.

Just wanted to post what fixed my problems, it's frustrating to see posts with same issues that you're having and not see a posted solution.